This invention relates generally to die cutting machines for making carton blanks, and in particular, to clamp pieces for interconnecting a grid network of bars to a frame assembly for a lower blanking tool that supports carton scrap during a blanking operation in a die cutting machine.
In the manufacture of cartons, small sheets of paper material having specific profiles are cut out of larger sheets of paper material. These smaller sheets are known as carton blanks that, in turn, are formed into cartons and/or boxes. The blanks are formed during a process known as a blanking operation in a die cutting machine.
In a die cutting machine, the blanks are cut, but not removed from a large sheet of paper material. After the blanks have been cut, the sheet is moved downstream in the die cutting machine to a blanking station where the sheet is positioned over a frame assembly for support. The frame assembly includes an outer frame and an inner grid having large openings that correspond in size, in shape and in position to the profile of the carton blank previously cut. Below the frame is a mechanism for stacking the carton blanks.
At the blanking station, an upper tool is used in combination with the lower tool or frame assembly to knock the carton blanks from the sheet of paper material while holding the scrap material that surrounds the blanks. The upper tool has a support board that moves vertically up and down in the die cutting machine, and the support board typically has a plurality of stand-offs depending therefrom that hold pushers spaced beneath the board which in turn are used to push the carton blanks from the sheet through the lower tool or frame assembly. A plurality of presser assemblies are also mounted in the support board and depend therefrom to hold the scrap material against the lower tool or frame assembly during the blanking operation so that the blanks may be pushed from the sheet. A presser assembly typically includes a presser rail which is biased downwardly away from the support board by a spring so that the rail is positioned slightly below the pushers. As the upper tool is lowered, the presser rail engages the sheet of paper material first such that a scrap portion of the large sheet of material is secured between the presser rail and the frame. The upper tool then continues to be lowered such that the sheet of material engages the inner grid within the frame while at substantially the same time the pushers engage the carton blanks and knock the blanks out of the sheet of material and through the inner grid. The carton blanks then fall into a stacking mechanism below the frame where the blanks are stacked for further processing.
The lower tool used in the blanking operation is typically comprised of a steel outer frame that supports an inner grid. The inner grid is typically comprised of a plurality of lengthwise and crosswise extending bars. In order to secure the inner grid in place on the outer frame, the ends of each bar are typically screwed onto attachment pieces which, in turn, are mounted on the lengthwise and crosswise rails of the outer frame. Since the frame and grid support a sheet of paper material during the blanking operation, the grid must be configured to match or conform to the die cut in the sheet of paper material. In addition, the grid must be reconfigured whenever a different carton blank needs to be produced. Thus, unscrewing the inner grid from the outer frame oftentimes becomes very cumbersome and time consuming. Thus, it is desirable to provide a quicker manner of attaching and removing the inner grid from the outer frame.
Therefore, it is a primary object and feature of the present invention to provide an improved clamp piece for interconnecting an inner grid of bars to a frame assembly for a lower blanking tool of a carton die cutting machine.
It is a further object and feature of the present invention to provide a clamp piece for interconnecting an inner grid of bars to a frame assembly for a lower blanking tool that allows for the inner grid to be easily attached and removed from its supporting outer frame.
It is a still further object and feature of the invention to provide a clamp piece for interconnecting an inner grid of bars to a frame assembly for a lower blanking tool which is compatible with standard blanking operation machinery and which is relatively inexpensive.
In accordance with the present invention, a clamp device is provided for attaching a bar of an inner grid to an outer frame for a lower blanking tool of a carton die cutting machine. The clamp device includes a plate member defining a vertically extending inner face, an opposite vertically extending outer face, a horizontally extending upper face having a cavity formed therein for receiving a portion of the bar and a bore extending between the inner face and the outer face along an axis at an acute angle to the outer face. A wedge member is pivotably disposed within the cavity. The wedge member is movable between a clamping position for retaining a portion of the bar in the cavity of the plate member and a release position. The wedge member includes a clamping surface engageable with the bar with the wedge member in the clamping position.
The cavity in the upper face of the plate member is defined by first and second spaced vertically extending sidewalls and a lower horizontal wall. A lower wall includes a depression formed therein for receiving a lower edge of the bar. A screw member moves the wedge member between the clamping and release positions. The screw member includes a fastener extending vertically through the wedge member along an axis perpendicular to the lower wall. In addition, the cavity includes a portion having a taer-drop shaped cross section at the inner section of the second wall and the lower wall. The wedge member includes a portion having a tear-dropped shaped cross section that is receivable in a tear-dropped shaped portion of the cavity. The clamping surface of the wedge member is generally arcuate and includes an apex. The acute angle of the bore extending between the inner face and the outer face of the plate member is preferably in the range of 30xc2x0 and 80xc2x0. In the preferred embodiment, it is contemplated that the acute angle be approximately 65xc2x0.
The outer face of the plate member may include a lip that is engageable with a corresponding ledge along the outer frame to support the plate member thereon. A fastening element extends through the bore in the plate member. The fastening element is receivable in a corresponding slot in the outer frame to interconnect the plate member to the outer frame.
In accordance with a still further aspect of the present invention, a clamp device is provided for attaching a bar of an inner grid to an outer frame for a lower blanking tool of a carton die cutting machine. The plate member defines inner and outer faces. The plate member has a cavity formed therein for receiving a portion of the bar and a bore extending between the inner face and the outer face along an axis at an acute angle to the outer face. A clamping structure is positioned within the cavity. The clamping structure is movable between a clamping position for obtaining the portion of the bar in the cavity of the plate member and a release position.
A plate member also defines a horizontally extending upper face and it is contemplated to form the cavity in the upper face. The cavity in the upper face of the plate member is defined by first and second spaced vertically extending sidewalls and a horizontal lower wall. The lower wall includes a depression for receiving a lower edge of the bar. The clamping structure includes a wedge member pivotably disposed within the cavity. The wedge member includes a clamping surface engageable with the bar with the clamping structure in the clamping position. The cavity also includes a portion having a tear-drop shaped cross-section at the intersection of the second sidewall and a lower wall. The wedge member includes a portion having a tear-drop shaped cross section that is receivable within the tear-drop shaped portion of the cavity. The clamping surface of the wedge member is generally arcuate and includes an apex. It is contemplated that the angle at which the bore extends between the inner and outer faces of the plate member be in the range of 30xc2x0 and 80xc2x0. Preferably, the acute angle is approximately 65xc2x0.
In accordance with a further aspect of the present invention, a frame assembly is provided for a lower blanking tool of a carton die cutting machine. The frame assembly includes a rigid outer frame and an inner grid comprised of a plurality of lengthwise and crosswise extending bars. A plurality of clamps attach the bars to the outer frame. Each clamp includes a plate member defining a vertically extending inner face, an opposite vertically extending outer face, and a horizontally extending upper face having a cavity formed therein for receiving a portion of the bar. A wedge is pivotably disposed within the cavity and is movable between a clamping position for retaining the portion of the bar within the cavity of the plate member and a release position.
The plate member of each clamp may include a bore extending between the inner face and the outer face thereof along an axis at an acute angle to the outer face. The acute angle may be in the range of 30xc2x0 and 80xc2x0. Preferably, the acute angle is approximately 65xc2x0.
The wedge member includes a clamping surface engageable with the bar with the wedge member in the clamping position. The clamping surface of the wedge member is generally arcuate and includes an apex. It is contemplated that the cavity include a portion having a tear-drop shaped cross section. The wedge member also includes a portion having a tear drop shaped cross section. The tear-drop shaped cross section of the wedge member is receivable in the tear dropped shaped portion of the cavity.